@irene so true, good thinking. Yes for after you have MAC, Im not sure, I feel meds or inhaling would be the best option but who knows, I havnt seen the DNA research.

I don't think that it would be necessary to vaccinate the whole world, nor that it would have to be administered after a person gets it. I think that we could make an analogy with the shingles/chickenpox situation (https://www.mayoclinic.org/diseases-conditions/shingles/symptoms-causes/syc-20353054), in that the vaccine against shingles is not given to the whole world but to those who are in higher risk groups. I think that in the same way that having developed a vaccine against chickenpox probably helped to develop a vaccine against shingles, the development of a vaccine against MAC could be aided by the experience with the vaccine against TB.
The demand for a vaccine against MAC has been increasing: In a 2011 paper (https://www.atsjournals.org/doi/full/10.1164/rccm.201111-2016OC) they studied a nationally representative 5% sample of Medicare Part B beneficiaries from 1997 to 2007, and found that the annual prevalence significantly increased from 20 to 47 cases/100,000 persons, or 8.2% per year. I wonder what has happened between 2007 and now, and compare it with, say, the increase in shingles.